Functional relationships in the nephrotic syndrome.

An analysis of 70 observations in patients with the nephrotic syndrome (NS) on a low sodium diet is presented. The following parameters were determined: plasma volume, plasma renin activity, plasma aldosterone concentration, serum albumin, urinary sodium and protein excretion, and creatinine clearance. In 41 instances glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined on the basis of 51Cr-EDTA and 125I-hippuran clearances, and the filtration fraction (FF) was calculated. The results in patients with minimal lesions (ML) and those with histological glomerular lesions (HL) were compared to determine whether these groups can be separated on the basis of signs of hypovolemia and primary renal sodium retention. Although a higher proportion of the ML patients showed extreme sodium retention and elevated plasma renin and aldosterone levels, these values tended to overlap and no differences were found for blood volume, blood pressure, and overall renal function between the groups. FF was markedly and equally depressed in both groups: 13.5 +/- 1.6% in the ML and 14.2 +/- 1.1% SEM in the HL group (NS). Analysis of the within-group relationships between the parameters under study revealed relatively few correlations, which supports the hypothesis that primary impairment of renal water and salt excretion is an important if not overruling factor in patients with the NS.